public class Solution1 {
    public static void main(String[] args) {
        int[] nums = {-1,0,3,5,9,12};
        int target = 9;
        System.out.println(search(nums, target));
    }
    public static int search(int[] nums, int target) {
        int left = 0;
        int right = nums.length - 1;
        while(left <= right) {
            // int mid = (right + left)/2; //有溢出风险
            int mid = left + (right -left) / 2;  //left + 区间总长度的一半  防溢出
            if(nums[mid] < target) {
                left = mid + 1;
            }else if(nums[mid] > target) {
                right = mid - 1;
            }else {
                return mid;
            }
        }
        return -1;
    }
}
